speeds up your bashrc by running (slow) setup commands on the fly
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Speed up your bashrc / zshrc: avoids running (slow) setup commands until you actually need them.


Having installed nvm, rvm, virtualenvwrapper and other similar gubbins over time, my shell starts horrifically slowly. By running these setup scripts on-demand, my time-to-first-prompt is nice and fast again. On top of this, I rarely need all of these tools enabled at the same time...


sandboxd creates a placeholder shell function for each command you specify (e.g. rvm). When this command gets run for the first time, the following happens:

  • the cmd placeholder function (plus all associated placeholders) gets removed
  • the setup you have associated with cmd gets run,
  • cmd gets run with the original arguments


To 'sandbox' a setup, wrap it in a function named sandbox_init_[name]:

# in ~/.bashrc / your shell rc file
source /path/to/sandboxd

# in ~/.sandboxrc
  source $(brew --prefix nvm)/nvm.sh #long running setup command

# create hooks for commands 'nvm', 'node' and 'nodemon'
sandbox_hook nvm node
sandbox_hook nvm nodemon
# this one not needed: it's created automatically based on the sandbox name
# sandbox_hook nvm nvm

The sandbox setup gets run once, when either nvm, nodemon or node is used for the first time:

[20:45:44 ~] echo 'console.log("hi")' | node
sandboxing nvm ...
[20:45:53 ~] echo 'console.log("hi")' | node

Manually calling the sandbox command

To manually run a specific sandbox setup, run sandbox [name]

This might be useful if you want to run a sandbox that doesn't have an associated command, or to create "feature flags" in your rc file:

#uncomment to enable features

# sandbox virtualenv
sandbox rvm
sandbox nvm